Comic strips are a good activity for students. They allow teachers to see if students understand the concepts taught in class. They also allow the students to show their creative side while having fun at the same time. The sites allow you to drag and drop characters, backgrounds, dialog boxes and add your text. They are very easy to manipulate. Here are 4 comic strip sites that are free and school friendly.
Superherosquad.marvel.com allows you to drag and drop super heroes (as the site name implies). This site also gives you the option to create a comic book. Pikikids.com gives you the option to upload your own photographs. The students could use their phones to take the pictures. The photography teacher in me advises you to teach your students about composition and lighting before you send your students out on their photo excursion. Makebeliefscomix.com allows the user to write the comic strip in English, Spanish, French, German, Italian, Portuguese or Latin. Pixton.com has a link for schools.
No matter what subject you teach, these comic strip sites give you the opportunity to assign a fun activity to your students.